No. 10. — Reports on the scientific results of the Expedition to the Eastern 

 Tropical Pacific, in charge of Alexander Agassiz, by the U. S. Fish 

 Commission Steamer "Albatross," from October, 1904, to March, 

 1905, Lieut. Commander L. M. Garrett, U. S. N., Commanding. 



XXIV. 



A peculiar form of Schizogony in Gonyaulax. 



By Charles Atwood Kofoid and E. Josephine Rigden. 



A single chain of Gonyaulax which presents unequivocal evidence 

 of a type of reproduction unknown elsewhere among the Dinoflagel- 

 lates occurs in the collections of the Expedition to the Eastern Tropi- 

 cal Pacific. Since so little is known regarding the process of repro- 

 duction in this order of Protozoa it seems advisable to place this case 

 on record and to note its relations to our meagre information on other 

 types known in the group. 



This chain was taken in the vertical haul of the No. 20 silk net made 

 October 13, 1904, at Station 4590, from a depth of 300 fathoms off 

 the Mexican Coast over Manzanillo Basin, 18° 58' N., 104° 50' W., 

 in surface temperatures of 82°-83°. It consists (Plate 1, figs. 1, 2) of 

 eleven individuals in chain, the sixth or middle member being the 

 largest, while the transdiameter of the individuals decreases quite 

 regularly towards either end. In the view presented in Fig. 1, 

 ventral for the distal members of the chain and oblique for the three 

 centrally located ones, the transdiameters are respectively 38, 39, 

 41, 45, 55, 68, 65, 57, 42, 40, and 27 /*, for the eleven members of the 

 chain. There is no proportionate decrease in the length of the indi- 

 viduals. They range from 25 to 35 jjl with the single exception of the 

 central member which is about 45 n long. The shorter members are 

 the more distal ones and those of the posterior half are somewhat 

 shorter than in the anterior half. The volumes, roughly computed, 

 run, from the anterior end posteriorly in the ratios of 3, 4, 5, 6, 9, 20, 

 13, 8, 4, 4, 2. The posterior five as a result of their greater trans- 

 diameters are thus somewhat larger, in spite of their lesser altitude. 



This greater size of the posterior members of the chain is often seen 

 also in Ceratium chains where the antapical horns are longer toward 

 the posterior and shorter toward the anterior end of the chain. See 



